Hi Megan,
I always find antique furniture to be really difficult to appraise online. You can’t see the details like wood joints and wood grain, plus there are some many styles and manufactures it’s very difficult to be a expert in all of it. That being said, please take this appraisal with a grain of salt, I’m absolutely no expert in antique furniture. However, in my opinion, I think your piece might be the style called French Renaissance and I would say the country of origin is the United States. I would need more details on the methods of construction and other details (circular saw marks or lack of them) such as dovetails or type of screws:
https://valuereview.com/dating-furniture/
The price range of antique sideboards is all over the place:
https://www.antiquesnavigator.com/common-price-guide.php?searchresults=yes&rpp=100&s1st=side&operator=and&s2=board&cat=Furniture&Search=Submit&pg=2
However, in my opinion your antique sideboard is valued around $400-600 dollars on these past sales:
https://www.antiquesnavigator.com/d-116699/horner-quality-heavily-carved-oak-sideboard-with-mirror.html
https://www.antiquesnavigator.com/d-79738/antique-french-renaissance-oak-buffet-sideboard-1880.html
I hope this information helps.
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